Transistor Help

I've been looking around online for at least 4 hours trying to get a straight forward answer on how to use a transistor. Right now I'm building a USB battery pack (Gets charged through USB and charges devices, such as an ipod, through the same usb port) and I need help choosing and hooking up the right transistors. BTW I want to use JFET transistors.

These are the questions:
1) I need to use them as switches, as in (I'm making this up, I need the real answers:
If it's a P-Channel it conducts if 5 volts is applied to the gate and
doesn't conduct when 0 volts is applied
If it's a N-channel it conducts if 0 volts is applied to the gate and
doesn't conduct when 5 volts is applied
2) Do i need resistors to keep the transistor for blowing up? What values and where do I place them?

3) I here you need negative voltage for some transistors, is it possable to convert + into -? Or can I just use the 5v as ground for that part of the circuit and ground as -5volts.


Also if someone could point me to a good, and I mean good website that covers everything on transistors that would be great. I'm talking about NFET and JFET and bipolar and everything!


Thanks in advance!

Do you want to use the transistors to switch power?

It sounds like you want power MOSFETs, not JFETs which are only used for amplifying small signals.

A voltage with the correct polarity on the gate of a Jfet turns it off. 0V at the gate to source turns it on. It doesn't conduct much current. its resistance is fairly high when it is turned on.

A voltage with the correct polarity on the gate of a Mosfet turns it on. A logic level Mosfet works with a gate voltage of 4.5V or more. 0V at the gate to source turns it off. A power Mosfet can conduct a huge amount of current and has a very low resistance when turned on.

So I need to use MOSFETs, is there a way to make it conduct when no power is applied and not conduct when 5v is applied?


EDIT: So there are 2 different modes, Depletion (Which I want for normally on) and Enhancment (Normally off), right?. What's the difference between N channel and P channel? I want to apply a positive voltage to the gate.

EDIT2: This might be a little much to ask, but can anyone help me find 2 cheap transistor on mouser? It needs to be able to turn/off at 5v. I want one to be normally on (connecting the drain and source) and normally off. From drain to source (or is it source to drain) it has to deliver 5v at 500mA

Depletion mode MOSFETs are normally used as small signal amplifiers.

Enhancement mode MOSFETs are used as high current switches or amplifiers.

You really haven't provided enough information about what you want to do with the transistors; where do you want to put the switch?

Here's a schematic of it, you can ignore the transistors, cause they're all wrong.

**broken link removed**


Basically it charges from a computer through a USB port, then you unplug it and it charges a usb device through the same usb port.

What the transistors do is change the input/output of the usb port.

Whenever the usb is plugged into a computer (by a male to male connector) the tranisistors Q1 and Q3 turn off (They are normally on, connecting the 2 batteries in parralel) from the Data+ port (5v), it also turns off Q4 (normally on) supplying the 5v to the usb port from the boost converter. The data+ also turns on Q2 transistor (delayed by the capacitor and resistor so that other transistors switch first) which connects +5 to the charging circuit.


So basically, computer = charge battery, Device (which doesn't supply the Data+ voltage) = Charge device from battery.

The IC arn't important, all they are are li-ion charger, battery protection, and step up dc-dc converter.


Whenever I finish this it'll be the smallest high capacity cheap usb charger ever! If i were to resell it... Whenever the batteries are connected in Parralel the combined energy will be 4800maH( **broken link removed**) (free shipping . That is a ton of energy compared to other things like minty boost which is only up to 2200 maH, plus it's rechargable.

Why didn't you upload your schematic to here? You uploaded it to a file storing service than makes everybody wait 30 seconds and wait another 30 seconds and wait another 30 seconds.

So I waited and waited and waited but I never got to the file.

A 100mA USB port will charge the 4800mAh battery is 48 hours. Nobody wants to wait that long.

I'm sorry, I didn't realize that this had a uploading thing, I'll upload it here. As for the 48 hours, yes I do realize that that's a long time, but I would probably charger it most the time through an ac to usb adapter supplying 200mA (it's what the chips are limited to) so that from a full discharge it would take 24 hours. This would be one of the battery things that you charge overnight, I mean this could charge an ipod at least 5 times, now who in the right mind would use an ipod that much in 1 day?



https://www.electro-tech-online.com/attachments/expresssch-pdf.13974/
ExpressSCH.pdf

note that all connected wires touch eachother and non connecting wires have an arc over the wire it's passing


EDIT: If I hook up the charging chip differently each chip would take 300 mA, combined to make 600mA, I need your opinion because a normal usb port only gives out 100mA and a High power one would give out 500mA, think it's too risky?

So a USB charger something like these ?https://www.mrgadget.com.au/catalog...echargeable-nimh-batteries-p-568.html?osCsid=.
https://www.thinkgeek.com/clearance/85be/
https://www.pccasegear.com/prod1270.htm